1. Field of the Invention
The present invention relates to a liquid crystal display device. In particular, the invention relates to a liquid crystal display device using an active matrix type liquid crystal display panel.
2. Description of the Prior Art
A liquid crystal display device comprises a liquid crystal display panel, a driving circuit, and peripheral devices such as backlight. A liquid crystal display panel of a typical liquid crystal display device of active matrix longitudinal electric field type (the so-called TN type) is prepared by sealing a liquid crystal between a first panel, which is made up by a first substrate (active matrix substrate or thin-film transistor substrate; TFT substrate) and a second panel made up by a second substrate (counter substrate or color filter substrate).
A new technique to provide a high-performance liquid crystal display panel at low cost is proposed in the Patent Document 1, for instance. In this technique, photolithographic process in the manufacture of the liquid crystal display panel is reduced by preparing various types of lines arranged on inner surface of the first substrate, and various types of electrodes and the pixel electrodes or semiconductor layers are prepared by ink jet method. To prepare the lines and the like by ink jet method, an insulating thin film (insulator film) is coated on inner surface of the substrate, and a pattern enclosed by bank-like members (also called “banks”) designed to follow the shapes of lines and electrodes is fabricated on the insulator film. In a region enclosed by the banks, a solution (conductive ink) with conductive particles dispersed in a solvent is coated by ink jet method, and then, baking is performed.
FIG. 27 is a schematical drawing to explain an example of a structure formed on inner surface of a first substrate by ink jet method. FIG. 28 is a flow chart to explain a process for forming the lines and the like by using the banks. In FIG. 27 and FIG. 28, photoresist is coated on inner surface of a first substrate SUB1, for which glass is used as a suitable material. The exposure to light is performed via a mask, which has patterns of the gate lines and the gate electrodes, and patterns of the capacity line. Then, these are developed, and the patterns of the gate lines, the gate electrodes and the capacity lines are removed, and the banks (gate banks) G-BNKs are prepared (bank patterning). Processing is performed in such manner that all portions inside the pattern of the gate banks G-BNKs have lyophilic property, and the other portions have liquid repellent property (lyophilic and liquid repellent processing).
A conductive solution (metal ink; e.g. an Ag ink with silver particles dispersed in it) is discharged and coated via ink jet (IJ) nozzle to the gate banks G-BNK. Then, by baking, the gate lines (not shown), the gate electrodes GT, and the capacity lines CT are obtained (by IJ discharge of gate lines/electrodes). Next, there is a process to obtain specific resistance of the line to a predetermined value by additional heating (metal baking (=bank additional heating)). It is desirable that the temperature of the additional heating to obtain specific resistance of the lines to a predetermined value is as high as possible.
On the contrary, the banks for forming the gate lines and the gate electrodes in lower layer of the pixel electrode (gate bank G-BNK) and the banks for forming the source/drain electrodes (source/drain banks SD-BNKs) are colored during additional heating when the lines are baked. To avoid the coloring of the banks, it is desirable to decrease the baking temperature of the lines to a value as low as possible.
[Patent Document 1] JP-A-2005-12181